The field of plasmonics exploits the unique optical properties of nanometallic structures to control and manipulate light at the nanoscale. Unlike glass, metals such as gold and silver have a negative dielectric function, which allows them to support collective electron excitations known as ‘surface plasmons’. These resonances produce extremely high local electric field intensities in localised regions.

Current Work

Nanoparticle-on-mirror plasmonic gapsWe study the fundamentals of plasmonic system and their coupling to molecular systems featuring nm-gaps exclusively formed via self-assembly. Here we mainly use nanoparticle-on-mirror (NPoM) geometry for controlled and reproducible gaps.

Conductive and quantum plasmonics Coupled plasmonic systems are similar to nanoscale plate capacitors with charges building up around the gap region. Only a small conductivity across this gap, either due to a conductive spacer or due to quantum tunnelling, disturbs this process by allowing a current to flow between the nanoparticle and the gold film. In this disturbed case new plasmonic modes emerge and evolve with changing conductivity, while at the same time the near-field intensity is greatly reduced due to screening by the currents.

Single molecule strong coupling Placing a single light-emitting molecule in a plasmonic gap changes its properties. We study the resonant electronic and vibrational coupling at the single-molecule level with carefully aligned molecular orientations in plasmonic nm-gaps using self-assembled monolayers. We aim to change the chemistry of single-molecules by modiyfing the coupling of electronic and vibrational states in <40nm3 plasmonic cavities and watch their dynamics in real time.

Previous Work

plasmonically-enhanced solar cells Using nanostructures which support strong localised plasmons, we are able to enhance the efficiency of ultrathin low cost solar cells by up to four times. This strategy can provide new routes to mass market photovoltaics.

plasmonic rolls of plasmeneJust a single layer of graphene can be rolled up to into carbon nanotubes, we have created plasmene sheets which can be rolled up to create plasmonic tubes. The colours of these tubes change with their morphology, and they can be rolled and unrolled by shining on light.

plasmonic sensing by RamanBecause the optical fields produced by plasmons are so strong, molecules in these fields can be detected extemely sensitively. The weak changes in colour of a scattered laser give the vibrational fingerprints of molecules. This allows to watch chemistry and nanoparticles on surfaces in exquisite detail.

surface-enahanced CARSThe strong optical fields in plasmons also allow the enhancement of a traditional molecular sensing technique called CARS, which uses multi-colour pulsed lasers. We demonstrate a new technique which million-fold enhancements allowing direct imaging, for instance of biosamples.

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